Stable isotope and hydrochemical signatures of massive ground ice on Herschel Island (Western Canadian Arctic)

• Main Authors: Fritz, Michael, Meyer, Hanno, Schirrmeister, Lutz, Lantuit, Hugues, Couture, N. J., Pollard, W. H.
• Format: Conference Object
• Language: unknown
• Published: 2009
• Subjects: Arctic; Beaufort Sea; Herschel; Herschel Island; Ice; Ice Sheet; permafrost; wedge*; Yukon
• Online Access: https://epic.awi.de/id/eprint/21427/; https://hdl.handle.net/10013/epic.33769

Herschel Island (69.583 °N; 139.083 °W) lies off the Yukon Coastal Plain in the southern Beaufort Sea as a terminal moraine resulting from the Laurentide Ice Sheet during the Early to Middle Wisconsin and represents the likely easternmost edge of Beringia.Massive ground ice bodies in the island's permanently frozen ground are ubiquitous and contribute to the shaping of the landscape since deglaciation. Stable water isotopes (δ18O, δD) have been analysed on various ground ice types. Since ground ice is a valuable record of climate information it can be used for palaeoenvironmental interpretation.Ice wedges on Herschel Island have begun to form in outwash and morainic deposits during the late Pleistocene after deglaciation, when dry and harsh climatic conditions promoted frost cracking. These ice wedges are remarkably depleted in their isotopic signature (δ18O of around −29 ) compared to Holocene ice wedges (δ18O of around 24 to 21 ).Within ice-rich permafrost sediments, also massive ice bodies are exposed whose appearance and isotopic composition is completely different from all other sampled ground ice types. Their δ18O records are strongly depleted (−33 ) thus suggesting a late Pleistocene origin. The slope and d-excess lie near the Global Meteoric Water Line (GMWL) indicating that the moisture source is likely of meteoric origin without substantial alterations. Other massive ice of unknown but supposedly glacial origin was encountered adjacent to large, striated boulders. With about −37 for δ18O, the ice exhibits extremely low isotopic values. The question arises, whether the ice bodies aggraded before or after deglaciation as massive segregated ice or if the ice was originally basal glacier ice buried by supraglacial till.Stable isotope geochemistry is limited to unravel the nature and origin of recovered ground ice. Therefore, hydrochemistry (pH, electrical conductivity, major ions) is used to differentiate between massive segregated ice, buried glacier ice and buried lake ice. Usually, buried ice types have ...